Telephone system



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l TELEPHONE SYSTEM Filed Aug. 23, 1939 16 Sheets-Sheet 15 IHI' ' /Nl/EA/TOR H. C. CAVE/@LV A 7' TOR/VEY Sept. 17, 1940- H, c. cAvERLY TELEPHONE SYSTEM Filed Aug. 23, 1939 16 Sheets-Sheet 16 /A/I/ENTOR y Heem/RLY A TTO/Q/VE Y Patented Sept. 17, 1940 UNITED STATES TELEPHONE SYSTEM Harry C'. Caverly, East Orange, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a. corporation of New York Application August 23, 1939, Serial No. 291,483

18 Claims.

This invention relates to telephone systems and more particularly to systems in which a charge is automatically made for each completed call in accordance with the relative location of the calling and called lines within the exchange area and in accordance With the elapsed conversational period.

In large exchange areas having several oices, some of which may be located at quite distant points in the area, it is desirable that means be `provided whereby a calling subscriber may be charged differently for calls to offices Which are most remotely located from the office in which the calling line terminates than for calls to ofces which are not so remotely located, since to reach such remotely located oflices, longer trunks and more switching equipment are required necessitating greater installation and maintenance costs. Furthermore, if such equipment is held in service on any call for long conversational periods, it is more equitable to the operating telephone company that the charges be also based on the length of the conversational period.

Heretofore, it has been proposed as disclosed in Patent 1,837,206, granted December 22, 1931, to Collis, to control the charging for calls on a zone and elapsed conversational period basis in small oiiice areas by providing the district selector circuits of all oices with equipment for timing the duration of calls and with equipment for controlling the subscribers message registers during the conversational period in accordance With the duration of the call and in accordance with the zone of the exchange area in which a call has been terminated. The addition of this equipment to every district selector in a large exchange area would be very expensive.

It is the usual practice in. large exchange areas, in order to reduce the expense of installation which would be incurred if direct interoflice trunks were provided between all oiiices of the area, to provide tandem offices located in different portions of the area to Which relatively short trunks from nearby oflices are extended and from which outgoing trunks ex-A tend to other oilices and through which calls may be trunked from one portion of the area to another. Since it is possible to trunk all interzone calls in this type of exchange system through the tandem ofiices, it then becomes possible to provide call charging facilities on a zone and elapsed conversational time basis by locating the timing and Zoning equipment in such tandem oices and to transmit message register control impulses as determined by such tandem oiice equipment over the trunk incoming from the originating office to relatively inexpensive equipment in the district selector circuits of the originating oice for controlling the subscribers message register.

It is therefore the object of the present invention to provide means for charging calls on a Zone and elapsed conversational period basis in large exchange areas which' is economical to install, operate and maintain.

This object is attained by the provision of timing and zone charging equipment associated with the district selector of the tandem ofiice in which each trunk incoming from an originating ofiice terminates, which equipment is operable in accordance with the duration of the call established over the trunk and in accordance With the zone of the exchange area in which both the calling and called lines terminate and Which is instrumental in transmitting message register control impulses over the talking conductors of the interoice trunk during the conversation to the district selector circuit in the originating oice. circuit of the originating office is provided with a gas-filled tube Which is responsive to the message register control impulses and in turn controls the message register of the calling line.

The district selector In the application of message register controlA tered in the usual manner in, the decoder, for

example as disclosed in Patent 1,840,132, granted January 5, 1932, to T. I-I. Roberts. The zone or dialing area in Which the calling line is terminated is determined by the particular interoiiice trunk over which the connection is e-x- Therefore, in accordance Withk tended to the tandem oflice and the zone classi iication thereof is transmitted to the decoder and registered therein by a group of relays. These relays in combination with the operated route relay determine the charging rate to be applied for any call by operating one of a plurality of rate register relays in the decoder. These rate register relays are then instrumental in selectively operating one or more rate relays in the zone and call duration equipment associated With the tandem district and interoiiice trunk employed in the connection.

Since the link circuit Which is employed in the tandem` ofce for associating the tandem district selector in which the incoming interoffice trunk ing in the decoder the dialing area or Zone inV which the calling line is located and for transmitting information from the decoder to theV district selector concerning the charge rate to be applied for the call, a district group connector is provided for establishing additional circuit paths from the decoder to the district selector. This connector comprises a plurality of district group relays one for each group oi one hundred districts or a maximum oi twelve and ten subgroup relays for each group relay or one relay for each subgroup oi' ten districts. A set of twelve district group relays is provided for each decoder and lock-out circuits are provided for preventing more than one decoder from obtaining access at any time to the same district group. For connecting a decoder with the same district selector which has been associated with an idle sender through the usual sender link, provision is made in the district to transmit signals of the well-known key pulsing character over the fundamental tip and ring conductors extended through the sender and decoder connector to registering relays in the decoder. These signals are instrumental in registering in the decoder the identification of the group of one hundred districts in which the district connected to the sender is located, the registration then being eiective to operate the appropriate one of the district group relays of the district connector. If the proper group relay is operated, a sig- -nal is sent back over the fundamental circuit conductors to indicate to the district that the proper group relay of the district connector has been operated, whereupon the subgroup relay in the district connector corresponding to the subgroup in which the calling district is located is operated from the district. Circuit paths are now extended from the zone and call duration equipment of the tandem district to the decoder over which the zone indication of the calling ofce is transmitted to the decoder and over which the rate relays of the equipment are selectively operated from the decoder.

The zone and call duration equipment of the tandem district comprises means for transmitting the district group identification signals to the decoder during the time that the sender registers are being set to record the called line number, means for recording the fact that the decoder has operated the proper group relay of the district connector and for operating the proper subgroup relay of the district connector, means for transmitting signals to the decoder through the district connector for registering in the decoder the zone from which the call has originated, register relays for registering the charge rate for the particular call as transmitted thereto through the district connector from the decoder and a st'ep-by-stepswitch for controlling the transmission of message register control impulses back over the interoice trunk for operating the calling subscribers message register in accordance with the rate registration set up by the rate relays. This switch is started to function upon the response of the called subscriber'y and during the rst half of its rst revolution transmits from one to eight impulses dependent upon the charge rate to be applied as registered by the rate relays. During the second half of its first revolution different intervals are measured for the initial period of conversation dependent upon the charge rate registeredrby lthe rate relays. Just prior to the completion oi its rst revolution an overtime relay is operated and thereafter upon each following complete revolution of the switch message register impulses are rst transmitted in accordance with the charge rate to be applied as registered by the rate relays for charging for an overtime period and then an overtime period is measured also dependent upon the condition of the rate relays.

In some instances the calling subscriber may desire the assistance of an operator in establishing a desired connection and in accordance with the usual practice dials zero whereupon the connection is established at the originatingy cnice to a trunk extending to an A operators. position.V The operator thereupon completes the desired connection.

, charge the calling subscriber for the call in accordance with the Zoning of the calling and called lines and in accordance with the elapsed time of the conversation, the trunk extending to the operators position is provided with equipment responsive to a charging key in the operatoris cord circuit for controlling the charging equipment of the originating district selector.

For a more complete understanding of the invention, reference may be had to the following detailed description thereof taken in connection with the accompanying drawings in which:

Fig. l shows schematically the equipment of an originating oice including the line of a calling subscriber, a line iinder, suchportions of a district selector circuit as are necessary to an understanding of the invention, an olice selector by means of which a call may be extended to any other ofiice of the exchange area, and the outgoing end of an interoce trunk extending to a tandem ofce;

Fig. 2 shows a district selector at the tandem cnice in which the interofce trunk terminates and which has access to other selectors for completing a desired connection;

Fig. 3 shows the message register control equipment appertaining to the district selector of Fig. 2;

Fig. 4 shows one of the senders of the tandem ofce indicated by the box and a schematic Irepresentation of the decoder-connector by a plurality of tandem district selectors with that one of a plurality of decoders which has been'.

taken for use on a call incoming to a tandem district selector;

Figs. 8 to 15 taken together illustrate such portions of one of the decoders as are necessary to an understanding ofthe invention;

Fig. 16 shows a trunk extending to an A operators position and the call charging equipment of an operators cord circuit; and,

Fig. 17 is a chart indicating the manner in l which the several figures of the drawings should be arranged to fully disclose the invention. i'

The invention has been embodied in a localy district selector circuit of the type disclosed in Patent 1,567,072, granted to W. H. Matthies on December 29, 1925, and in tandem ofiice circuits,"

of the type disclosed in Patent 1,840,132, granted To enable the operator to January 5, 1932, to T. H. Roberts, above referred to.

EsTABLIsHMENT or CONNECTION To THE TANDEM OFFICE It will be assumed that the subscriber at substation initiates a call by removing his receiver from the switchhook whereupon an idle line finder |01 associated with a district selector |02 is started to hunt for and seize the calling line. Thereafter the line-nder, district-selector link IUI-|02 becomes associated in the wellknown manner with an idle sender |03 as, for example, over la link circuit such as is disclosed in the patent to Matthies above referred to. The calling subscriber upon receiving a dial tone from the sender then proceeds to dial the office code and numerical designations of the wanted line resulting in the registration vof such designations in the sender. It will be assumed that the desired line terminates in a distant office of the exchange area and that, therefore, in response to the registration of the oice code designations of the wanted line number, the sender proceeds to set the district selector |02 and the office selector |04 to select an idle trunk such as |05 extending to a tandem oilice through which the desired line may be reached.

Upon the seizure of the idle trunk, a relay is connected across the tip and ring fundamental circuit conductors |06 and |01 at the sender |03 completing a circuit from the district selector at the tandem office which may be traced from battery through resistance lower back contact of relay 302, lower winding of retard coil 303, conductor 304, upper Winding of relay 200, left contacts of cam 203, upper normal contacts of relay 202, tip conductor of the interofce trunk, through the sender, thence over the ring conductor of the trunk, lower normal contacts of relay 202, lower left and upper rightcontacts of cam 20|,

. lower winding of relay 200, conductor 305, upper winding of retard coil 303, upper back contact of v relay 302, through resistance 300 to ground. Relay 200 operates, closing a circuit from battery through the winding of relay 204, contact of relay 200, conductor v205 to ground over the upper right contact of cam 301. Incidentally, it may be stated that the sequence switch cams disclosed in both Figs. 2 and 3 are controlled by the sequence switch magnet 360 disclosed in Fig. 3. Relay 204 upon operating disconnects ground from conductor 20B to mark the district selector as calling to the district finder of the link circuit indicated by the small box 350 in Fig. 3 and closes an ob-l vious operating circuit for relay 201. Relay 201 upon operating connects ground from the upper back contact of relay 308, over conductor 208, upper back contact of relay 209, lower front contact of relay 201, right contacts of cam 2|0 to start conductor 2| l for starting an idle Alink circuit to select the calling district selector as identiiied by the removal of ground from conductor 206 and to select an idle sender. The operation of the link circuit to accomplish these functions is fully described in the patent to Roberts hereinbefore referred to.

As soon as the district selector circuit has been found, ground is connected to conductor 300 at the link circuit thereby completing a circuit from such conductor over the inner upper back contact of relay 308, conductor 2|2, lower right and upper lef-t contacts of cam 2|3 through the lower winding of relay 200 to battery. Relay 209 upon operating locks over its inner lower front contact, the upper right contact'of camv 2|4 'and the .upper left contact of cam 2|5 to ground; disconnects ground from the start conductor 2| and establishes a circuit from ground'over conductor 200, upper front contact of relay 200, conductor After it leaves position 1, the lowerwindf ring conductor of the interoflice trunk and theupper winding is connected over the upper right`- contact of cani 220, the upper left contact of cam 230, the inner upper back contact of relay 225, and the upper right and lower left contacts of cam 203 to the tip conductor of the trunk whereby relay 200 is maintained operated until after the sequence switch leaves position 3. Upon reaching position 2, ground is connected over the lower right contact of cam 2|1, conductor 2|8 and the left contact of cam 3| to conductor 206, to prevent the selection of the district selector by any other district lfinder and when the sequence switch leaves position 2, the locking circuit of relay 200 is opened and relay 209 releases. When the sequence switch reaches position 3, relay 308 operates in a circuit from battery through its winding, conductor 3|2, right contacts of cam 2|0, conductor 220, lower back contact of relay 209, upper right contact of cam 2M, to ground at the upper left contact of cam 2|5; removes ground from the upper armature of relay 209, and connects the winding of relay 3|3 over either its inner lower or upper front contacts and conductors 309 or 3|4 through the link circuit to the sender 400 of Fig. 4, as soon as the sender is fao selected by the link circuit, as determined by the" cross-connections of the cross-connecting block g 3|5, and connects one of several different combinations of high o1' low resistance battery or ground to conductor 309 or 3|4 as determined by the cross-connections of the cross-connecting block 3|5 to indicate to the decoder the group of one hundred districts in which the calling district is located as will be later described.

When the sender has Abeen found, it connects mediumresistance to ground through the link circuit to conductor 3|0 thence over the upper right contact of cam 3|1, conductor 22|, through the winding of relay 222 to battery and over the upper left contact of cam 3H and conductor 223 through the upper winding of relay 224 to battery. Relay 222 operates but relay 2214 being miarginal does not operate at this time. Relay 222 upon operating establishes the circuit of relay 225 extending from battery through the winding of yrelay 225, conductor 220, the left contacts of cam 338, conductor 221, contact of relay 222 to ground whereupon relay 225 operates, at its upper back contacts disconnects the windings of relay 200 from the trunk conductors and connects the trunk conductors over its upper front contacts through the link circuit to the sender, the tip conductor of the trunk being connected as previously described to the inner upper armature of relay 225, thence over the front Contact thereof, the lower left and upper right contacts of cam 23|, upper back contact .of relay 232, conductor 233, thence through the link to the sender and the ring conductor of the trunk being connected as previously described to the upper armature of relay 225, thence over the front contact thereof, the upper left and lower right contacts of cam 234, lower back contact of relay 232, inner upper back contact of relay 22d, conductor 235, thence through the link to the sender. Relay 200 is now held operated under the control of relay 222 in a circuit extending from battery as traced through the upper winding of relay 200, inner lower front contact of relay 207, lower front contact of relay 225, conductor 236, right contact of cam SHS, lower left Contact of cam 33B,

A conductor 22? to ground at the front contact of relay 222.

The disconnection of the windings of relay 200 from the trunk conductors is a signal to the sender |03 of the originating ollice to commence the transmission of pulse code impulses to the tandem sender 400 to transfer the ofiice code and nun merical designations of the wanted line registered therein to registers of the tandem sender. As soon thereafter as the office code has been transferred to the oiiice code registers of the tandem sender, the tandem Ysender operates relay 10i which in turn operates the multicontact relay 402 individual to the sender of the decoder-connector 050 after which the multicontact relay 403 of the decodereconnector individual to an idle decoder, assumed to be the decoder disclosed in Figs. 8 to l5, inclusive, is operated. With relays 402 vand 403 both operated, a plurality of control paths are established between the sender r400 and the decoder in the manner fully described in the Roberts patent hereinbefore referred to. Upon the connection of the sender to the decoder, the operation of relay 008 connects ground to conductor H0 thereby operating the decoder start relay |200. Conductors 309 and 3M are now extended through the link circuit and over conductors 000 and Ml' included in the 4cable 405 extending from the link circuit 350 to the sender 500, thence over contacts of relays '402 and 003 of the decoder-connector to conductors 408 and 009. Fundamental tip conductor 408 is further extended over the middle upper back contact of relay 800, lower back contact of relay 80! and thence serially through the winding of polarized relay 802, upper winding of marginal relay 803, winding of relay 80d, resistance 805 to batter-y and fundamental ring conductor 009 is further extended over the inner upper back Contact of relay 800, upper back contact of relay 801, winding of polarized relay 800, upper winding of marginal relay 801,

f ground to either or both of the fundamental tip and ring conductors 309 and 3M dependent on the cross-connections on the block 348l for identifying the group of one hundred tandem district selectors in which the calling tandem district is located. The cross-connections may be made4 from full battery or ground to terminal 3l!) of the block which is connectedto one terminal" of the winding of relay 3l3; from high resistance battery or high or low resistance groundv to ring terminal 320 which is connected by relay 308 to the fundamental ring conductor Sllor high resistance battery or high o r low resistance ground to tip terminal 32! which is connected by relay 308 to the fundamental tip conductor 300 and the other terminal of the winding of relay 8l3 may be connected to either terminal 320 or 32! to identify twelve groupsl of districts in accordance with the following table:

Table I Hundred dis- Terminal 321 Terminal 320 tricts Termmal 319 fundamental tip fundamental ring 1st group Ground Relay 313 2nd group d Relay 313. 3rd group 4th group do Relay 313. 5th group Ground Relay 313 High resistance at r 6th group do High resistance Relay 313.

attery. 7th group Battery Relay 313 Low resista-nce ground. 8th group do High resistance Relay 313.

battery. 9th group Ground. Relay 313 Low resistance ground. 10th group do Low resistance Relay 313.

ground. 11th group Battery Relay 313 Low resistance ground. 12th group do Low resistance Relay 313.

ground.

In the decoder relays 802, 803 and 800 selec- Table II Register Dliglggup Circuit condition on tip 408 Circuit condition on ring 409 Pglsys relays p operated lst group High resistance ground 804 812 2nd group 808 815 802, 804 810 High resistance battery- 806, 808 813 High resistance ground 802, 804, 808 810, 815

High resistance battery 802, 804, 806, 808 810,813

High resistance ground.. Low resistance ground S0 807, 808 812, 814

10th group `flow resistance ground High resistance ground 3, 804, 808 811,815 11th group High resistance battery. Low resistance ground 802, 804, S07, 808 810, 814 12th group Low resistance ground High resistance battery. 803, 804, 806, 808 811, 813

winding of relay 808 through resistance 809 to battery.

ASSOCIATION oF TANDEM DISTRICT WITH SEIZED DECODER It will be recalled that at the tandem district selector, relay 308 upon operating connected a combination of high or low resistance battery or located in the rst group of one hundred districts il 

